The aim of this supplementary document is to provide the supporting assessment methodology, relevant legislation and bibliography used for the creation of the main Biodiversity Net Gain (BNG) report.
The intention is to enable the main report to be as easy as possible to read, to help with understanding the conclusions, impacts, and recommendations made.
BNG is a specific, measurable outcome of project activities that deliver demonstrable and quantifiable benefits to biodiversity compared to the baseline situation. In order to achieve BNG, a project must be able to demonstrate that it has followed all 10 of the Principles of Biodiversity Net Gain (as outlined in the British Standard 8683:2021 Process for Designing and Implementing Biodiversity Net Gain).
The legalised Environment Act (2021) requires developments in England to demonstrate a measurable net gain in biodiversity and sets a target of a minimum of 10% BNG for all developments. It also stipulates that a management plan with a minimum 30-year term, should be adopted to ensure biodiversity net gain can be delivered. The. The requirement for biodiversity net gain is enshrined within the Environment Act (2021) and the National Planning Policy Framework (NPPF, 2024).
The Statutory Biodiversity Metric is the widely accepted tool used to calculate BNG. It enables the calculation of habitat value pre- and post-development in order to determine the overall change in biodiversity value as a result of the proposed development. The Biodiversity Metric has separate BNG assessments for areas of habitat, hedgerows and watercourses. The biodiversity value of a site should be maximised. However, it may not always be possible to achieve a 10% biodiversity net gain within a site and therefore the Statutory Biodiversity Metric can also account for offsite habitat creation, where land is available. Alternatively, developers can seek to provide an agreed financial contribution to an appropriate third party (such as the Local Authority, the UK Government or another landowner) to deliver the required biodiversity net gain elsewhere on their behalf.
Habitat Area/Length (baseline and post development)
The area or length of each habitat was calculated using qGIS software. In calculating the area or length of each habitat, habitats which occur as two or more isolated parcels across the site were combined, where they were deemed to be of a similar composition and condition. Distinctions were made between habitats to be retained (i.e. left as found in baseline), enhanced (i.e. improved condition) or lost (i.e. destroyed by proposed development).
Areas of scattered trees were calculated using the Tree Helper tool within the Statutory Biodiversity Metric. Class sizes for urban trees are set out in Table 14 of the Statutory biodiversity metric: user guide (DEFRA, 2024).
Habitat Condition (baseline and post development)
Baseline habitat condition was assessed using the relevant condition assessment sheets found in The Statutory Biodiversity Metric – Technical Annex 1: Condition Assessment and Sheets and Methodology (DEFRA, 2024).
Post development habitat condition was determine using the Temporal Multipliers Tool and the Enhancement Temporal Multipliers Tool included in the Statutory Biodiversity Metric spreadsheet as well as the relevant condition assessment sheets found in the Statutory biodiversity metric: user guide (DEFRA, 2024). These are also based on the assumption that a 30-year management plan will be adopted for the site.
Strategic Significance (baseline and post development)
Strategic significance should be primarily informed by the Local Nature Recovery Strategy (LNRS) for the site and its LPA. At present, however, few have been drafted and none have been formally published. As such, the application of strategic significance as set out in Table 7of the statutory biodiversity metric user guide (DEFRA, 2024) has not been followed.
Some responsible authorities have specified the use of alternative interim documents. In those cases, such interim documents were consulted, and the qualifying factors set out in Table 8 of the statutory biodiversity metric: user guide (DEFRA, 2024) were followed. Where the responsible authority has not provided alternative interim documents to use, relevant local planning policies were used to determine strategic significance.
Beyond the LNRS and local policies, priority habitats as defined by the UK Biodiversity Action Plan (UKBAP, 2007) have automatically been assigned ‘high’ strategic significance.
Degradation
Historic aerial satellite images of all sites were assessed via GoogleEarth to inform whether habitat degradation had occurred.
Condition of habitats subjected to degradation was determined based on the availability of historic ecological and/or arboricultural data. Where no previous data was available, all habitats subject to condition assessments were conservatively determined to have achieved ‘good’ condition as to not undervalue the habitats lost. Where data, however complete, was made available, assumptions about conditions will have been made and justified in the report bodies.
BNG Mitigation Hierarchy
BNG should be achieved in a way that is consistent with the mitigation hierarchy, the levels of which in decreasing order are:
Justification to how the BNG mitigation hierarchy has been adhered to is outlined in the report bodies.
The Environment Act 2021 (EA 2021) received Royal Assent on 9 November 2021 and became fully mandatory on 12th February 2024 for major developments and 2nd April 2024 for minor developments. The Act principally creates a post Brexit framework to protect and enhance the natural environment. Through amendments to the Town and Country Planning Act 1990, the Act will require all planning permissions in England (subject to exemptions which is likely to include householder applications) to be granted subject to a new general pre-commencement condition that requires approval of a biodiversity net gain plan. This will ensure the delivery of a minimum of 10% measurable biodiversity net gain. The principal tool to calculate this will be the Statutory Detra Biodiversity Metric (DEFRA 2024). Works to enhance habitats can be carried out either onsite or offsite or through the purchase of ‘biodiversity credits’ from the Secretary of State. However, this flexibility may be removed (subject to regulations) if the onsite habitat is ‘irreplaceable’. Both onsite and offsite enhancements must be maintained for at least 30 years after completion of a development (which period may be amended).
The National Planning Policy Framework promotes sustainable development. The Framework specifies the need for protection of designated sites and priority habitats and species. An emphasis is also made on the need for ecological infrastructure through protection, restoration and re-creation. The protection and recovery of priority habitats and species (considered likely to be those listed as species of principal importance under Section 41 of the Natural Environment and Rural Communities (NERC) Act 2006 is also listed as a requirement of planning policy.
In determining a planning application, planning authorities should aim to conserve and enhance biodiversity by ensuring that: designated sites are protected from harm; there is appropriate mitigation or compensation where significant harm cannot be avoided; measurable gains in biodiversity in and around developments are incorporated; and planning permission is refused for development resulting in the loss or deterioration of irreplaceable habitats including aged or veteran trees and also ancient woodland.
Section 40 of the Natural Environment and Rural Communities (NERC) Act 2006, requires all public bodies to have regard to biodiversity conservation when carrying out their functions. This is commonly referred to as the ‘biodiversity duty’.
Section 41 of the Act requires the Secretary of State to publish a list of habitats and species which are of ‘principal importance for the conservation of biodiversity’. This list is intended to assist decision makers such as public bodies in implementing their duty under Section 40 of the Act. Under the Act these habitats and species are regarded as a material consideration in determining planning applications. A developer must show that their protection has been adequately addressed within a development proposal.
The aim of this supplementary document is to provide the supporting survey methodology, relevant legislation and bibliography used for the creation of the main Baseline Condition Habitat Assessment (BCHA) report.
The intention is to enable the main report to be as easy as possible to read, to help with understanding the conclusions, impacts, and recommendations made.
The BCHA report describes the baseline ecological conditions at the site, specifically for the purpose of informing the Biodiversity Net Gain (BNG) Assessment for the site.
To achieve this, the following steps have been taken:
A survey plan and location map are presented in the report, along with a proposal plan (where available).
The methodology for this baseline survey is based on the best practice publication UK Habitat Classification Documents (UKHAB) V2.01 (July 2023). All land parcels are described and mapped according to the appropriate habitat classification including primary and secondary codes where required. Where appropriate, target notes provide supplementary information on habitat conditions, features too small to map to scale, species composition, structure and management.
Baseline habitat condition was assessed using the relevant condition assessment sheets found in The Statutory Biodiversity Metric – Technical Annex 1: Condition Assessment and Sheets and Methodology (DEFRA, 2024).
The Environment Act 2021 (EA 2021) received Royal Assent on 9 November 2021 and became fully mandatory on 12th February 2024 for major developments and 2nd April 2024 for minor developments. The Act principally creates a post Brexit framework to protect and enhance the natural environment. Through amendments to the Town and Country Planning Act 1990, the Act will require all planning permissions in England (subject to exemptions which is likely to include householder applications) to be granted subject to a new general pre-commencement condition that requires approval of a biodiversity net gain plan. This will ensure the delivery of a minimum of 10% measurable biodiversity net gain. The principal tool to calculate this will be the Statutory Detra Biodiversity Metric (DEFRA 2024). Works to enhance habitats can be carried out either onsite or offsite or through the purchase of ‘biodiversity credits’ from the Secretary of State. However, this flexibility may be removed (subject to regulations) if the onsite habitat is ‘irreplaceable’. Both onsite and offsite enhancements must be maintained for at least 30 years after completion of a development (which period may be amended).
The National Planning Policy Framework promotes sustainable development. The Framework specifies the need for protection of designated sites and priority habitats and species. An emphasis is also made on the need for ecological infrastructure through protection, restoration and re-creation. The protection and recovery of priority habitats and species (considered likely to be those listed as species of principal importance under Section 41 of the Natural Environment and Rural Communities (NERC) Act 2006 is also listed as a requirement of planning policy.
In determining a planning application, planning authorities should aim to conserve and enhance biodiversity by ensuring that: designated sites are protected from harm; there is appropriate mitigation or compensation where significant harm cannot be avoided; measurable gains in biodiversity in and around developments are incorporated; and planning permission is refused for development resulting in the loss or deterioration of irreplaceable habitats including aged or veteran trees and also ancient woodland.
Section 40 of the Natural Environment and Rural Communities (NERC) Act 2006, requires all public bodies to have regard to biodiversity conservation when carrying out their functions. This is commonly referred to as the ‘biodiversity duty’.
Section 41 of the Act requires the Secretary of State to publish a list of habitats and species which are of ‘principal importance for the conservation of biodiversity’. This list is intended to assist decision makers such as public bodies in implementing their duty under Section 40 of the Act. Under the Act these habitats and species are regarded as a material consideration in determining planning applications. A developer must show that their protection has been adequately addressed within a development proposal.